Java 如何使用JAXBContext将单例对象保存到XML文件？

我希望使用JAXBContext将单例对象保存到XML文件中。所讨论的对象称为Player，它扩展了一个抽象类实体。实体也扩展线程。因为Player是一个单例对象，所以它的构造函数是私有的，并且不可从类外部访问。 我怎样才能正确地做到这一点

下面是我用来保存玩家的代码：

public static void savePlayer() throws JAXBException {
        JAXBContext context = JAXBContext.newInstance(Player.class);
        Marshaller m = context.createMarshaller();
        m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        OutputStream os = null;
        try {
            os = new FileOutputStream(StringConstants.PLAYER_SAVE_FILE);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        m.marshal(Player.getInstance(), os);
    }

下面是再次读出的代码：

public static Player readPlayer() throws JAXBException {
        JAXBContext context = JAXBContext.newInstance(Player.class);
        Unmarshaller u = context.createUnmarshaller();
        File f = new File(StringConstants.PLAYER_SAVE_FILE);
        return (Player) u.unmarshal(f);
    }

在实体和玩家这两个职业上，我都使用了以下涂鸦：

@XmlRootElement

里希特开始上课了

以下是我得到的错误输出：

com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException: 1 counts of IllegalAnnotationExceptions
java.lang.Thread$UncaughtExceptionHandler is an interface, and JAXB can't handle interfaces.
    this problem is related to the following location:
        at java.lang.Thread$UncaughtExceptionHandler
        at public java.lang.Thread$UncaughtExceptionHandler java.lang.Thread.getUncaughtExceptionHandler()
        at java.lang.Thread
        at model.entities.Entity
        at model.entities.Player

    at com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException$Builder.check(IllegalAnnotationsException.java:91)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getTypeInfoSet(JAXBContextImpl.java:445)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.<init>(JAXBContextImpl.java:277)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.<init>(JAXBContextImpl.java:124)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl$JAXBContextBuilder.build(JAXBContextImpl.java:1123)
    at com.sun.xml.internal.bind.v2.ContextFactory.createContext(ContextFactory.java:147)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:247)
    at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:234)
    at javax.xml.bind.ContextFinder.find(ContextFinder.java:462)
    at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:641)
    at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:584)
    at model.io.SaveWriter.savePlayer(SaveWriter.java:20)
    at tests.SaveTest.main(SaveTest.java:17)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)
com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException: 1 counts of IllegalAnnotationExceptions
java.lang.Thread$UncaughtExceptionHandler is an interface, and JAXB can't handle interfaces.
    this problem is related to the following location:
        at java.lang.Thread$UncaughtExceptionHandler
        at public java.lang.Thread$UncaughtExceptionHandler java.lang.Thread.getUncaughtExceptionHandler()
        at java.lang.Thread
        at model.entities.Entity
        at model.entities.Player

    at com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException$Builder.check(IllegalAnnotationsException.java:91)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getTypeInfoSet(JAXBContextImpl.java:445)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.<init>(JAXBContextImpl.java:277)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.<init>(JAXBContextImpl.java:124)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl$JAXBContextBuilder.build(JAXBContextImpl.java:1123)
    at com.sun.xml.internal.bind.v2.ContextFactory.createContext(ContextFactory.java:147)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:247)
    at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:234)
    at javax.xml.bind.ContextFinder.find(ContextFinder.java:462)
    at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:641)
    at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:584)
    at model.io.SaveReader.readPlayer(SaveReader.java:18)
    at tests.SaveTest.main(SaveTest.java:23)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)

---

我终于找到了问题所在。如问题中所述，类播放器扩展了类实体。类实体扩展了公共线程类。显然，不能为线程对象正确实例化JAXBContext。我通过让类实体实现可运行的接口解决了这个问题，这使我不再有任何错误。

您在播放器类设置器中使用了@XmlElement注释吗？你需要准确地标记你想要的东西。您可以在本教程中找到更多信息：到目前为止，我没有，因为Player类目前没有setter，除了它扩展的Entity类中的setter。我认为问题在于JAXBContext的实例化。Player和Entity类都缺少公共构造函数。我尝试应用您提到的注释，但这并没有改变错误日志中的任何内容。